[Style API] Adds usePluginStyle hook and PluginStyle type

[alisonjlai]

Adds a new style API with

• Add style on PluginInstance. Defines the PluginStyle type, currently supporting backgroundColor.
• getStyle() – fetches the current style config via wb:plugin:style:get
• subscribeToStyle() – listens for live updates via wb:plugin:style:update
• Implements a usePluginStyle() React hook

Will update readme when this is finalized.

Sample plugin app:

function App() {
  const styleColors = usePluginStyle();

  return (
    <div
      style={{ backgroundColor: styleColors?.backgroundColor }}
    >
        ...
    </div>
  );

[peternandersson]

super small, can we just call these subscribe and get? Makes more sense to do style.subscribe() than style.subscribeToStyle()

[peternandersson]

Can you change getStyle to get?

[peternandersson]

Otherwise, LGTM

[peternandersson]

Suggested change

	subscribe(callback: (style: any) => void) {
	subscribe(callback: (style: PluginStyle) => void) {